Take it from me, I was Xbox Live's number 1 account jacker at one point (Predator)
This is definitely not original. It may be a word, and it may be a 1 letter. But it's not original unless it's a commonly used word that is used in every day life.
Well, that's just my definition. I've had tags like: Predator, Alien, Cash, Rain, Doom, ect... And that's just a short list of them.
My understanding of an OG is that a singular word with out a prefix or suffix. Just because it's not known doesn't mean it is not an OG. It maybe a shitty OG but a OG gamertag non the less.